The present invention relates to an exposure apparatus. More particularly, the present invention relates to an exposure apparatus used for exposing a pattern onto a flat substrate for fabricating a flat panel such as a liquid crystal display panel and a plasma display panel.
Display qualities of recent liquid crystal display panels and plasma display panels are remarkably enhanced. Moreover, the liquid crystal display panels and the plasma display panels are thin and light, and thus are becoming major image display apparatuses as substitutes for CRTs. Particularly, a direct-view type active matrix liquid crystal panel is making progress in enlarging its screen size, and to that end the size of glass substrates used for fabricating the liquid crystal panels are becoming larger as well.
As an exposure apparatus for exposing element patterns of a display panel onto a large-sized glass substrate, a scanning-type exposure apparatus is known. The scanning-type exposure apparatus performs exposure by synchronously scanning a photomask or a reticle having a pattern formed thereon (hereinafter, referred to as a xe2x80x9cmaskxe2x80x9d) and a glass substrate applied with a photosensitive agent such as a photoresist (hereinafter, referred to as a xe2x80x9csubstratexe2x80x9d).
When a photosensitive agent such as a resist is applied onto a substrate by, for example, a spin coater or the like, the resist often leak into the periphery of the back surface of the substrate. When such substrate with the resist on its back is loaded on a substrate holder of the exposure apparatus, the substrate-holding surface of the substrate holder is contaminated, and the back surface of the substrate and the substrate-holding surface of the substrate holder may not contact closely to each other causing a problem of poor flatness of an exposure area of the substrate.
According to a scanning-type exposure, the number of scanning steps may increase depending on the size of the device pattern and the size of the substrate, which may result in poor throughput. As an example, a scanning-type exposure of a substrate to a mask pattern at one to one magnification size will be described.
Assume that the size of effective exposure area of the mask is 400 mmxc3x97700 mm, the size of the substrate is 720 mmxc3x97900 mm, and the size of a substrate holder for holding the substrate is 843 mmxc3x97890 mm (the whole surface of the substrate holder consists of a vacuum-holding surface). A scanning-type exposure apparatus, which synchronously transfers a mask stage (for supporting and transporting a mask) and a substrate stage (a substrate holder for supporting a substrate), with respect to a projection optical system, is used to expose a pattern of a 17-inch SXGA liquid crystal display panel onto a substrate. The size of the 17-inch SXGA panel including a circuitry pattern surrounding a pixel region is 279.7 mmxc3x97347.2 mm.
The size relationship is shown in FIGS. 13 and 14. FIGS. 13 and 14 are schematic views showing the sizes of a rectangular substrate holder 15a and a substrate 200 held by the substrate holder 15a (which is represented by dotted lines in FIG. 14 for distinction from the substrate 200), respectively. As shown in FIG. 14, the substrate 200 is loaded on the substrate holder 15a such that the longer sides of the substrate 200 are arranged along the longer sides of the substrate holder 15a. 
FIG. 15 is a schematic view for illustrating a manner of printing six 17-inch SXGA panels on the above-described substrate by using a mask 100 which has two 279.7 mmxc3x97347.2 mm circuit patterns 101 formed thereon. In FIG. 15, the substrate holder 15a is omitted.
With reference to FIG. 15, a pattern exposure for fabricating a 17-inch SXGA liquid crystal display panel is carried out as follows. First, a first scanning exposure is conducted by synchronously transferring the mask 100 and the substrate 200 in the X-direction as indicated by an arrow 1 to print two circuit patterns 101 on exposure areas 200a and 200b of the substrate 200.
Then, the mask 100 and the substrate 200 are transferred back to the exposure initiating positions to perform a second scanning exposure to print a single circuit pattern 101 on an exposure area 200c as indicated by an arrow 2. Since the length of the side of the substrate 200 is 900 mm, two circuit patterns 101 cannot be exposed at the second scanning exposure.
Next, while the substrate 200 is step transferred in the Y-direction, the mask 100 and the substrate 200 are transferred back to the exposure initiating positions to perform a third scanning exposure to print a single circuit pattern 101 on an exposure area 200d of the substrate 200 as indicated by an arrow 3. Finally, two circuit patterns 101 are printed on exposure areas 200e and 200f as indicated by an arrow 4.
According to such a conventional exposure method, even when the mask 100 is provided with two circuit patterns 101, there is a case where only a single circuit pattern 101 can be printed at a time. As a result, the number of scanning exposure increases, limiting improvement of the throughput.
In view of the current situation of exposure apparatuses, the present invention has an objective of providing an exposure apparatus in which the flatness of a substrate is not deteriorated with a photosensitive agent leaking into the back surface of the substrate, or in which a surface holding the substrate is not contaminated by the same. The present invention also has an objective of providing an exposure apparatus which requires less number of scanning steps and which has improved throughput without any device enlargement.
According to the present invention, a substrate-holding surface of a substrate holder is provided with grooves with which a periphery of a substrate make contact so that a photosensitive agent leaking into the back surface of the substrate can escape into the grooves. Furthermore, a structure of the present invention allows a substrate to be placed in sideways with respect to a substrate holder (placing the longer sides of the substrate in parallel to the shorter sides of the substrate holder) depending on the size of the apparatus and the size of the substrate. Where the substrate is placed in sideways with respect to the substrate holder, it is acceptable even when areas other than an effective exposure area should project out from the substrate holder, since there is no need of precisely controlling flatness of areas of the substrate where no pattern is to be printed.
Along with the reference numerals, the present invention is an exposure apparatus that exposes a pattern of a mask (10, 30) onto a substrate (14), comprising: a substrate holder (15a) having a substrate-holding surface to hold the substrate, the substrate-holding surface being provided with a first pair of grooves (31, 32) extending from one end to the other along a first direction (X-direction) and a second pair of grooves (33, 34) extending from one end to the other along a second direction (Y-direction) substantially perpendicular to the first direction; and a substrate stage (15) that supports the substrate holder to move in the first direction (X-direction).
The first grooves (31, 32) and second grooves (33, 34) are positioned such that they make contact with the periphery of the substrate (14) when the substrate (14) is vertically or horizontally placed on the substrate holder (15a). According to this structure, even when a photosensitive agent leaks into the periphery of the back surface of the substrate (14), the resist escapes into the first and second grooves (31, 32; 33, 34), thereby preventing deterioration of the flatness of the substrate (14) or contamination of the substrate-holding surface of the substrate holder (15a). The distance between a pair of first grooves (31, 32) may be equal to the length of the shorter sides of the rectangular substrate (14).
The exposure apparatus may be provided with a first holding member (60, 61, 62) to hold the substrate (14) at a first region (41, 42, 43) of the substrate-holding surface defined by the first pair of grooves (31, 32), and a second holding member (60, 61, 63) to hold the substrate (14) at a second region (41, 44, 45) of the substrate-holding surface defined by the second pair of grooves (33, 34). The exposure apparatus may further be provided with a selector (50) that selects one of the first holding member (60, 61, 62) and the second holding member (60, 61, 63).
The substrate holder (15a) is provided with a plurality of adsorbing pores on its substrate-holding surface. The plurality of adsorbing pores are provided over a plurality of regions which are defined by the first pair of grooves (31, 32) and the second pair of grooves (33, 34), and are selectively connected to a vacuum source (60) such as a vacuum pump with the first vacuum-holding members (60, 61, 62) and the second vacuum-holding members (60, 61, 63). The first vacuum-holding members (60, 61, 62) are used to vacuum hold the substrate (14) placed between the first pair of grooves (31, 32), while the second vacuum-holding members (60, 61, 63) are used to vacuum hold the substrate (14) placed between the second pair of grooves (33, 34). The selector (50) for selecting the first vacuum-holding members (60, 61, 62) and the second vacuum-holding members (60, 61, 63) can comprise a controller that controls opening and closing of an electromagnetic valve.
The exposure apparatus of the invention is an exposure apparatus for exposing a pattern of a mask (10, 30) onto a rectangular substrate (14), the substrate (14) being loaded on a substrate-holding surface of a substrate holder (15a), comprising: a substrate stage (15) capable of moving in a first direction (X-direction) while supporting the substrate holder (15a); and a detecting device (65, 66) for detecting whether the substrate (14) is loaded on the substrate-holding surface such that the longer sides of the substrate (14) are arranged along the first direction (X-direction). The detecting device (65, 66) can be realized with a contact switch provided on the substrate-holding surface of the substrate holder (15a), vacuum sensors provided in the middle of vacuum lines connecting with the vacuum pores in the substrate-holding surface. The substrate holder (15a) is rectangular, and a shorter side of the substrate holder (15a) is set shorter than the longer side of the substrate (14).
There is no need of precisely controlling the flatness of the areas of the substrate (14) where they are not exposed to a pattern of the mask (10, 30). Accordingly, when the substrate (14) is placed in sideways with respect to the substrate holder (15a) whose shorter sides are shorter than the longer sides of the substrate (14), it is acceptable even when areas other than the effective exposure area of the substrate (14) should project out from the substrate holder (15a). Since such non-exposed areas are allowed to project out from the substrate holder (15a), the exposure apparatus can be made small.